The influence of polymeric matrix structure on the kinetic and thermomechanical properties of organic-inorganic composites based on TEOS

Abstract

A promising trend in modern material science is the development of new composite materials based on organicinorganic systems with unique characteristics that combine the properties of individual components. Hybrid organicinorganic composites based on the system of mono-or dimethacrylate and tetraethoxysilane (TEOS) were synthesized. The influence of the structure of the polymer matrix (2-hydroxyethyl methacrylate (HEMA) or oligoesteracrylate (MGF-9)) and the composition of relates hybrid systems on thermomechanical properties and molecular structure of the resulting composites and kinetics of polymerization till deep conversion has been studied. The synthesis of composites was carried out via the process of simultaneous polymerization of the mixtures of liquid organic and inorganic components, during which the inorganic structure is formed in situ in the polymer matrix. The kinetics of stationary photoinitiated polymerization of monomer-tetraethoxysilane systems in thin films till deep conversion was investigated by laser interferometry. The experimental integral and differential kinetic curves were obtained and kinetic parameters of photoinitiated polymerization of the studied systems were determined. As a result, the dependence of the values of the maximum rate of polymerization, conversion and time of its achievement on the ratio monomer : tetraethoxysilane in the compositions was revealed. The kinetic features of polymerization of mono-and dimethacrylates were described using the concept of microheterogeneity of the process of photoinitiated polymerization till deep conversion. The thermomechanical analysis determined the characteristic temperatures, the values of the thermomechanical structural-molecular parameters of the composites were calculated as well. It was shown that when introducing an inorganic filler into a matrix of monomethacrylate, the linear growth of the thermomechanical stability of the material can be observed depending on the quantity of TEOS, while in the case of dimethacrylate matrix this dependence can be characterized by the presence of an extremum, which is related to the formed composites. It was found that HEMA : TEOS = 95 : 5 vol. % and MGF-9 : TEOS = 90 : 10 vol. % composites have the improved thermomechanical properties.The obtained composites can be perspective for the use as a protective coating, in particular for solar collectors, and a basis for the manufacture of conductive membranes for fuel cells.